January 14, 2010

How often patients receive surveillance colonoscopy may need to be better aligned with their risks for colorectal cancer, according to two papers published this month by University of Pittsburgh School of Medicine researchers. The studies provide evidence that colonoscopy is both overused and underused in particular patient populations with serious implications for health care spending.

According to Robert E. Schoen, M.D., M.P.H., professor of medicine and epidemiology at the University of Pittsburgh and senior author of both papers, surveillance colonoscopy is performed to monitor patients who have had precancerous polyps, called adenomas, found on a previous colonoscopy. The aim of surveillance is to identify and remove recurrent growths before they advance to cancer.

"Guidelines recommend that patients who have had pre-cancerous lesions, especially advanced precancerous lesions, get follow-up colonoscopy earlier and more often than patients who do not have polyps," said Dr. Schoen. "Yet our studies show surveillance colonoscopy is not being used by the medical system in relation to underlying risk."

The first study, published in the January edition of the journal Gastroenterology, demonstrates a substantial overuse of surveillance colonoscopy among low-risk patients and under-use among high risk patients. The study followed 3,600 patients from the National Cancer Institute (NCI)-sponsored Prostate, Lung, Colorectal and Ovarian (PLCO) cancer screening trial. Among 1,026 patients with no precancerous lesions at their initial examination, 58 percent underwent a follow-up exam an average of every 3.9 years, although the recommendation would be to do so every five or 10 years. Detailed review of the records could not identify medical reasons for the premature testing. After five years, only 58.4 percent of patients with advanced precancerous lesions received surveillance colonoscopy despite the recommendation that they do so every three years.

"High-risk patients aren't receiving timely follow-up colonoscopy but there is over-utilization among low-risk patients who are unlikely to develop colon cancer," Dr. Schoen said. "This misuse wastes health care resources and risks development of cancers in high-risk patients that might have been preventable." The second study, published in the January issue of GIE: Gastrointestinal Endoscopy, emphasizes a persistent, ongoing risk of cancer, despite colonoscopy, especially among patients with a history of advanced precancerous lesions.

For the study, 1,297 individuals who participated in the NCI's Polyp Prevention Trial, a four-year study which examined the effect of a low-fat, high-fiber, high-fruit and vegetable diet on precancerous polyp recurrence, were followed for an additional six years. Nine cases of colorectal cancer developed although the individuals had multiple colonoscopies during the 10-year observation period. Seven out of the nine subjects who developed cancer had a history of advanced precancerous lesions.

"Despite regular colonoscopy, colorectal cancer may still occur. This study emphasizes that patients with a history of advanced polyps are at particular risk and should be monitored closely with timely surveillance examinations," said Dr. Schoen. "Combined, these studies seriously indicate how surveillance colonoscopy is being implemented, and represent a call-to-action to align colonoscopy use with patient risk, especially in an era where we are trying to spend our health care dollars as effectively as possible."